"The well-recognized mode of transmission of HEV, since the first historical outbreak of HEV in 1951 in India, is waterborne transmission by drinking fecally contaminated water," lead author Dr. Eyasu H. Teshale from Centers for Disease Control and Prevention, Atlanta, Georgia, told Reuters Health by email. "Person-to-person transmission of HEV was discounted by many investigators in the past in locations mainly where studies occurred in an area endemic to HEV."

The outbreak lasted from October 2007 to August 2009 and involved more than 10,000 cases. In a February 23rd online paper in Clinical Infectious Diseases, Dr. Teshale and colleagues report findings from the epicenter of the outbreak, the Madi Opei "Internal Displaced Persons" camp in northern Uganda. In 2008, the international aid group Doctors Without Borders described Made Opei on its web site as "...an ocean of small mud huts....(People are) living in makeshift shelters with poor sanitation facilities and little freedom of movement."

During active case finding in Madi Opei between October 2007 and June 2008, nearly a third of the 10,535 residents (3218, 30.5%) had jaundice, and two thirds of the 237 participants in the seroprevalence survey (161, 67.9%) had evidence of recent or past HEV infection, including 105 with antibody profiles indicating recent infection.

Roughly three quarters of the Madi Opei residents with jaundice (2476, 76.9%) lived in households with more than one case. Among these individuals, 1280 (51.7%) were index cases or occurred within 2 weeks of the index case in the same household, 580 (23.4%) occurred within 2 to 8 weeks of the index case, and 616 (24.9%) occurred more than 8 weeks after the index case.

Households with more than one case were more likely to have members who had close contact with a jaundiced person, attended a funeral for someone who died with jaundice, or regularly washed their hands in communal basins. People in those households were also less likely to have washed their hands after defecation.

Water samples from the two protected borehole wells used by the residents were negative for HEV RNA, and only 2.5% in the seroprevalence survey admitted drinking water from a source other than these wells.

"In Uganda, we looked at transmission from animals (pigs) to humans, but pigs carried a different genotype (GT 3) that was not related to human cases during this outbreak," Dr. Teshale said. "To date, there is no evidence of interspecies transmission of GT 1 HEV between humans and pigs."

"The outbreak spread fast, overwhelming the traditional prevention and control interventions," Dr. Teshale added. "We believe, in such settings vaccination will be the best tool to control outbreaks before large morbidity and mortality occur."

Until a vaccine becomes available, however, "provision of good sanitary facilities and clean water" as well as "education about the role of communal food and handwashing basins in spreading HEV" are critical, the article concludes.